In 1983, 900 individuals 55 to 64 years of age were randomly drawn from the population registry of Telemark county, Norway. 400 of these were invited to a flexible sigmoidoscopy screening examination, and 400 individuals were not offered any screening. In 1996, the remainder, both cohorts from 1983 were invited to a colonoscopy screening examination. A new age and sex matched control group, not being offered screening, was randomly drawn from the same registry. Both groups are to be followed with regard to CRC incidence, CRC mortality and all-cause mortality through national Norwegian registries.